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By Kellie E. Gagnon, Aidan Hodge, John Vaught, Kelli Gagnon

The USACE geologists at the Bluestone Dam Phase 5 Dam Safety Assurance (DSA) Megaproject in Hinton, WV have employed the use of Terrestrial LiDAR scanning and photogrammetry for the purpose of mapping and documentation of stilling basin foundation conditions. Following the excavation and cleaning of a 60-foot by 60-foot monolith foundation, a Trimble SX-10 scanning total station is used to capture high density 3D scans, imagery, and survey measurements of the monolith floor and adjacent side walls. This data is used to generate high density point clouds of the entire foundation and sidewalls, which in turn facilitate the creation of numerous products that aid in the documentation and future assessment of the project foundation. These products include high resolution true color orthophotos, detailed topographic maps, excavation reports, and 3D models. Quarter scale orthophotos of the foundation and sidewalls are printed out and used as base maps for geological field mapping, allowing for greater accuracy and faster execution time when compared to traditional field mapping methods. Topographic maps, orthophotos, and data obtained from excavation reports contribute to the generation of detailed and accurate Foundation, Completion, and Geotechnical Reports, and will help inform the project Post Implementation Evaluation (PIE). Annotated 3D models, with the future incorporation of virtual/augmented reality technology, will allow design personnel, project delivery teams, and risk assessment teams to virtually inspect bedrock conditions and better identify any underlying geological conditions that impact post-construction performance of the project. This innovative approach has allowed project geologists to exceed the requirements for foundation mapping and documentation as outlined in ER 1110-2-1156. The quality and volume of spatial and geological data collected using this method has allowed for a faster and more efficient foundation approval process, reducing the time during which the foundation is exposed during construction and lowering risk at the project.

Oct 7, 2024

By Brian Metcalfe, Kord Wissmann, Gianni Martinez

The Middle East consists of vast deserts that reach temperatures up to 50°C (122°F), with some areas characterized by endless sand dunes. When project team members selected the location for a large new transportation project, little did they know that the site would be characterized by soft, nearly normally consolidated silt and clay extending below a thin sand crust. Searching for solutions, the design team elected to reinforce the sub­surface with rammed aggregate pier ground improvement elements and wanted verification that the method would stand the test of prolonged static loads. Because the concrete pave­ments would serve to spread the load, a "zone load test" was performed, consisting of applying a uniform bearing pressure of 150 kPa (22 Psi) over a 7.5 m (25 ft) square concrete footing. Unlike individual pier load tests, the zone test allowed the project engineers the opportunity to confirm design parameter values under large­loading area conditions, a situation not often available to most designers. This paper presents the results of the zone load test, which may be interpreted to better understand design parameter values, and is of particular significance because it adds a valuable contribution to the relatively few numbers of "group load tests" available in the literature for ground im­provement applications.

Feb 1, 2024

By Desi Dikova, Daniel Wagstaffe, Lori Simpson, Eric Lindquist

1621-1629 Market Street is a mixed-use development in the South of Market district of San Francisco, located directly above Bay Area Rapid Transit (BART) tunnels and alongside the San Francisco Municipal Railway (MUNI) tunnels that run below Market Street. The project included the construction of five new buildings up to nine stories tall, each with single-level basements, supported on improved ground. The project transformed a cluster of commercial buildings and surface parking lots into residential, retail and office buildings, and publicly accessible open spaces. Subsurface conditions at the site include uncontrolled fill, loose sand, and marsh deposits, with groundwater approximately 15 feet deep. Engineering challenges faced during design and construction included: protecting the tunnels beneath and adjacent to the site; the presence of uncontrolled fill, loose sand and potentially liquefiable soil; the phasing of multiple, non-concurrent basement excavations; and construction in a dense urban area, including protection of both on-site and neighboring buildings and other improvements. In addition to Building Code requirements, the project complied with BART’s stringent requirements on loading, settlement, vertical and horizontal movement control, groundwater control, and limiting tieback lengths to provide clearances to tunnels and utilities. This paper reviews these challenges, with a focus on the temporary support of excavation (SOE) systems and the ground improvement. The SOE systems consisted of deep soil mixing (DSM) cutoff walls for four of the buildings and soldier-pile-and-lagging for the other; all were restrained by tiebacks or internal bracing. The DSM walls were incorporated into SOE systems for neighboring buildings with each phase, resulting in efficient shoring utilization. The ground improvement consisted of an interconnected grid of DSM panels that mitigated liquefaction and extended building loads to a dense sand layer. Load testing of DSM elements was performed to confirm adequate bearing capacity.

Oct 7, 2024

By Valerie Vasquez, Howard Perko

Construction of large-scale battery energy storage systems (BESS) is becoming prevalent throughout the United States to meet demands of the electric grid and optimize effectiveness of alternative energy sources. Helical pile foundations are regularly used for support of battery containers and transformers.  This type of foundation system is reuseable and sustainable, and is advantageous because of its ability to carry high axial loads at relatively low cost. This paper presents multiple case histories of BESS supported on helical pile foundations and explores the design and implementation aspects of helical piles. Case histories include several sites in Texas, one in Mississippi, and one in Nevada. The quantity of individual BESS units at each site ranged from approximately fifty to two-hundred.  Each individual unit was supported on six or eight helical piles, resulting in thousands of helical piles utilized across all sites. For design, the feasibility of using helical pile foundations is first considered by review of the site-specific geotechnical report.  A boring analysis is constructed. If the project site is suitable for helical pile foundations, an initial helix sizing is performed. Given the dimensions and weight of the BESS units and environmental factors, the required helical pile loads and layout is developed. Helical pile capacity can be verified based on torque correlations. To confirm the helical pile design is acceptable, test installation programs are implemented at each site. The purpose of the test is to measure the depth at which the required installation torque is achieved. Based on the data collected, helical pile length is optimized across the subject site. If site grading has not been performed prior to the test installation, adjustments are made to account for expected cut/fill. This method of optimization through field testing results in an economic and speedy foundation system for rapid deployment of BESS.

Oct 7, 2024

By Liz Smith

The I-35 NEX project is a $1.6 billion design-build in northeast San Antonio in an area with known karst features. The project involves single-column, nonredundant, large diameter shafts that support an elevated highway. This case history describes the site reconnaissance, field investigation, design evaluations, and construction challenges. 

Oct 7, 2024

By Michael Arnold, Oliver Kaden, Cyril Bou Sleiman

In the framework of the Herbert Hoover Dike Rehabilitation project, BAUER Foundation Corp. had been tasked with the installation of 17.5 miles (28 km) of seepage cutoff wall distributed over three task orders.  The cutoff wall is 50 to 65 feet (15 to 20 m) deep and minimum 24 inches (0.61 m) wide. Beside numerous connections to existing concrete structures and existing cutoff wall segments, the work included the connection of the cutoff wall to three utility pipes at pump station S-131: one 96-in (2.44 m) diameter corrugated metal pipe (CMP) and two 48-in (1.22 m) steel pipes. The cement deep soil mixing method of Cutter Soil Mixing (CSM) has been used to install the wall.  The contract documents stipulated the use of jet grouting for all pipe connections.  The large diameter and the deteriorated state of the CMP caused the contractor question whether it would be feasible to meet strict contract requirements for the interface utilizing jet grouting methods. The contractor prepared a value engineering cost proposal (VECP) to avoid jetting around the CMP. The proposal included an excavation shored using sheet piling and soldier piling, partial removal of the CMP, jet grouting below the CMP, reconnection of the CMP, backfilling with controlled low strength material (CLSM), jet grouting around the steel pipes and finally CSM tie-ins into the CSLM block and jet grout cutoff wall. The paper introduces the project, the existing conditions, the geotechnical site conditions and the requirements specified by USACE.  It describes the pursued approach, the equipment used, and auxiliary measures needed to facilitate the approach.  Strength and permeability results are presented. The paper also discusses challenges encountered and related lessons learned.

Oct 7, 2024

By Jonathan Ernst, John Regan, Leo Hart

Originally built in 1856, the existing bridge carries 5 railroad tracks servicing MNRR and AMTRAK and spanned over Atlantic Street in Stamford, CT providing two (2) lanes of traffic beneath the bridge.  Replacement of the bridge was driven by several factors including age, traffic improvements to widen the narrow underpass to service 5 lanes of traffic and increase headroom beneath the bridge to reduce restrictions on larger vehicular traffic.  The proposed pile supported bridge abutments were designed to be constructed while keeping all 5 railroad tracks in service, creating a need for individual jumpspan girder systems beneath each track.  A temporary excavation support system (SOE) design was included in the Contract  and consisted of drilled H-piles soldier piles and bracing with bolted connections.  GTR re-designed the SOE system to accommodate low headroom restrictions and constructability issues associated with track outages and site logistics.  Several key factors were to be considered for the SOE system: (1) headroom restrictions beneath catenary systems, (2) train axial, lateral, braking and traction forces, (3) headroom during pile cap construction, (4) integrating the SOE system to accept the “jump span” bridge components, and (5) Phased construction considerations.  To address these factors, GTR designed an SOE employing drilled micropile load bearing soldier piles with internal bracing to tunnel beneath the active railroad traffic.  This SOE scheme was successfully installed in low headroom conditions beneath existing  catenary lines in five (5) phases and included an innovative pre-fabricated bearing connection “top hat” to accept the jump span bridge.  Each phase of work was successfully installed and completed to support each active railroad track in five - 9-day outages. To achieve the required excavation support, a detailed phasing plan was required to support each adjacent track as subsequent jump span bridges were installed.  Although tedious excavation and bracing installation process was required, supporting the railroads required a robust system to ensure the safety of the workers and rail traffic alike.  After the SOE and jump span bridges were installed, the abutment foundations were constructed beneath the jump span bridges and between the SOE’s. Careful analysis and planning allowed for the creation of an accurate and precise system to support the axial and lateral train pressures while performing the required construction under the rail traffic.  This paper presents a unique case study of the “tunneling” beneath active railroad tracks utilizing a temporary support of excavation system to construct proposed pile supported abutments.

Oct 7, 2024

By Jerry Dimaggio, Ahmad A. Alhasan

With the increased vulnerability of transportation infrastructure to extreme events, resilience of transportation and infrastructure assets has become more critical. The term geotechnical asset applies to all infrastructure features constructed on, in, or of soil and rock. Depending on a specific application, a “geotechnical asset” may serve as a foundation of an asset, the asset itself, or both. This extent and variability of type (walls, slopes and structural foundations) makes them the most critical and challenging assets to manage and maintain. Moreover, geotechnical assets are vulnerable because of the number of internal asset variables and their susceptibility to accelerated moisture, erosion, and environment-related changes, which directly or indirectly impact the asset performance. This paper discusses the workflow and components of a recently developed resilience-based design framework of geotechnical assets. The core concept in Resilience-Based Design is to model the asset performance over time including possible repeated extreme events. These events result in accumulated progressive damage and accelerate the deterioration of the asset leading to progress serviceability or strength failure. The framework focuses on capturing the impacts of damage on the assets performance and incorporating preventive and corrective maintenance during the asset service life. The Resilience-Based Design (RBD) framework was then contrasted to the Allowable Stress Design (ASD) and Load and Resistance Factor Design (LRFD) frameworks in a significant case study of a soil slope stabilized using anchored drilled shafts. The slope was monitored over an extended period of time to capture the creep deformations of the stabilized slope. The design procedure will model multiple flood events using weather models developed for the area. Following the detailed case study example of the framework, the paper discusses the needs and procedures to implement the framework for a wide range of applications.

Oct 7, 2024

By Karla Myers, Howard Perko

Foundation designs utilizing helical pile groups are increasingly widespread in the electric power utility industry.  Yet the application of these systems lacks uniformity and knowledge gaps may exist. Recently, a body of codes and practice documents have been prepared by DFI and ASCE subcommittees regarding standard practice for electric power transmission structures design.  These codes and standards are discussed as they apply to helical pile groups.  With a better understanding of how the codes apply to these foundation types, engineers and designers can more confidently and adeptly specify and bid from a broader range of deep foundation options. Design of electric power transmission structures is most challenging at angles, water crossings, and dead ends.  These structures often are characterized by large overturning moments. This presentation will cover simple hand calculations for estimating the distribution of pile reactions from ground line tower moments.  Then, pile groups modeling using Ensoft® Group will also be covered in depth and with specific design examples from real case histories.  Design considerations for sizing of individual piles and key differences between pile design for building structures and pile design for power transmission towers and applicable codes and standards will be discussed.  Preliminary findings from field measurements performed on existing helical pile group supported structures, if available, may be included as they relate to validation of models.

Oct 7, 2024

By Seth Robertson

Instrumented static load testing is an effective means for assessing load-transfer characteristics of augered cast‑in‑place piles under static axial load. Strain gauges are typically instrumented on the steel reinforcement at specific locations along the pile’s embedded length for determining geotechnical resisting forces in side-shear and end-bearing. Conversion of strain to internal force at each gauge level can be complicated, requiring critical assessment of the pile properties and potential strain-dependent behavior. Current codes and standards provide recommendations for approximating these necessary pile properties, although these methods may not routinely yield realistic interpretation of measured strains. Non-linear rigidity may be exhibited over a static load test duration and there remains limited published methods for determining load-distribution characteristic under these conditions. Through measuring embedded strain and uniaxial stress simultaneously, the pile’s strain-dependent rigidity can be directly determined, thus minimizing uncertainty in the analytical process. While not commonly implemented in standard load test practices, stressmeters have been installed adjacent to strain gauges for this reason. A case study is presented where stressmeters were specially adapted for installation on augered cast-in-place piles on a bi‑directional static load test program. Based solely on the measured strains, it was realized that a non-linear rigidity would be required for properly converting strains to internal forces. The uniaxial stresses determined from the stressmeter measurements provided valuable insight in the pile material response to applied loads, ultimately reducing to a non-linear piecewise function of rigidity versus strain. Derivation of this non-linear piecewise function and methodology for computing internal forces are addressed. Comparisons of the non‑linear rigidity function to alternative rigidity (linear and non-linear) determination methods are presented. Recommendations for improving instrumented static load tests are summarized, primarily focusing on prospects and interpretation of embedded stressmeter measurements in top-down and bi‑directional static load tests.

Oct 7, 2024

By Melinda Hummel, Howard Perko

Colorado has a diverse geology including alluvial, colluvial, and eolian deposits overlying sedimentary, metamorphic, and igneous bedrock at varying depths and outcrops.  There is often concern for helical piles bearing on bedrock in these soil profiles, particularly if the bedrock is sloping or too hard to penetrate.  Though it has been accepted for a long time that helical pile axial capacity is correlated with installation torque, there are sometimes concerns regarding helical piles that refuse or “spin-out” on bedrock without meaningful torque readings.  This paper covers common practices in the industry for design of helical piles end bearing on bedrock.  Hardness of bedrock and penetrability of helical piles into bedrock are presented.  Design choices that can be used to help improve penetration are discussed.  Common approaches to estimate capacity of helical piles that “spin-out” and other concerns for helical piles end bearing on bedrock are described.  Keywords End Bearing, Helical Pile, Bedrock

Oct 7, 2024

By Rebecca Hurley

Spring in the state of Kentucky brings every climate possible within a matter of weeks. Typically, the initial thaw from winter occurs followed by flash flooding rain. The heat is kicked up for a few random days just for the semi-dried soil to be washed away by another torrent of rainfall. Judging by the last few years, a round of tornadoes can also be expected to make an appearance. Haunting fog will plague the hollers in the evening, veiling the missing roadway washed away earlier that day. This creates an interesting obstacle course of dodging cliffs, cones, cars and the occasional ATV. Of course, a threat is posed to all the residents and travelers of the failed roadways. These rural area do not have the luxury of multiple access roads to their homes. Roads with a major failure preventing even a single line of traffic to pass through are deemed emergency projects and are prioritized to begin construction. This sequence of events took place in the early part of 2023 on a rural road in Harlan County, Kentucky, and this case study describes the processes and methods that allowed rapid response for reconstruction of the failed roadways.

Jun 1, 2024

By Derrick Dasenbrock

Geotechnical engineers are usually well-acquainted with contractual and noncontractual documents used to convey geotechnical information in a construction project - typically sub-surface exploration logs, engineering and geology reports, project plans, and contract specifi­cations. Both owners and contractors rely on com­plete , appropriate and accurate information in contract and informational documents to achieve the successful delivery of projects, com- municating requirements to meet budget, schedule, safety, performance and other goals. Traditionally, contract documents have been created and delivered through paper plans and reports or electronic paper equivalents such as PDFs. Geotechnical information is often included in these documents in an unstructured format. Geotechnical requirements may be shown on the plans, or included in the project special provisions, standard provisions or gov­erning geotechnical agency manuals. Simplified geotechnical logs may appear on plan sheets with more complete logs available elsewhere. Additional documents may reference field, lab, geologic, materials or other additional reports, which are often neither readily available to on-site workers nor contractual in their nature. Nearly always, geotechnical infor­mation is provided in a static format, rather than as structured digital data, decreasing its utility to contractors for bidding, design analysis and con­structabilityevaluations.

Nov 1, 2024

By Aneesh Goly

In the dynamic landscape of foun­dation engineering, where precision and reliability are paramount, recent technological advancements have heralded a new era of sophistication and efficiency. At the core of this transformation is the integration of artificial intelligence (AI), the Internet of Things (IoT) and embedded data collectors (EDCs), each playing a pivotal role in redefining traditional practices. The current state of foundation en­gineering is one characterized by a heightened emphasis on data-driven decision-making, predictive analysis and enhanced safety protocols - all underpinned by these technological innovations. The impact of AI, IoT and EDCs on foundation engineering is profound. AI algorithms, with their capacity for processing vast amounts of data, offer unprecedented insights into soil be­havior and structural integrity. loT brings a new dimension of connectivity, enabling real-time monitoring and communication between various components of a construction project. EDCs, integral to this network, provide the crucial data that fuels both AI analyses and IoT efficiency. Together, these technologies are not just add-ons but have become fundamental to the field's advancement. This article aims to delve into the synergy of AI, IoT and EDCs within foundation engineering, exploring how their integration is shaping the future of the industry. We will trace the evolution of foundation practices from their traditional roots to their current state­of-the-art incarnations, highlighting how these technologies are driving the field towards more efficient, safe and sustainable practices.

Apr 1, 2024

By Dominik Gächter, Wojciech Szczepinski, Jakub Bieszczad

Increased requirements for rail transport north of Oslo have forced Norwegian Authorities to invest in the development of double-track rail to decrease traveling time and increase the frequency of the rail service. Part of this development is Tangenvika Bridge which is built on the largest lake and drinking water reservoir in Norway (Mjøsa). Once completed, it will be the longest railway bridge in Norway. The foundation design consists of drilled and driven composite piles. All the works are performed on water and because of its depth, all piles are installed from floating container pontoons instead of jack-up barges. In order to meet the strict steel quality requirements of composite piles, all piles are welded on land in a controlled environment and then transferred onto the transfer pontoons on water. Close to shores, due to the local presence of sensitive soils and the risk of underwater landslides, a total of 78 drilled piles (1016mm) are executed using the reverse circulation method (RC). All piles are drilled 2m into bedrock using a fully integrated ring bit system. In the deepest parts of the lake, a total of 60 driven piles (1430mm) are installed using 350kJ hydrohammer. The bottom of the piles are finished with a closed-ended pile tip, which is the most popular driven pile tip in Norway. All drilled and driven piles are installed in single lengths of up to 85m and net weight of 102t at 1:5 inclination. The lifting process of the piles on the water provides significant challenges for which a combination of 400t crane, 2 transfer pontoons, and a tugboat is used to provide a safe execution method.

Oct 7, 2024

By M. Tangstad, M. Zhu, M. B. Folstad

The dissolution rate of silica (SiO2) into different compositions of SiO2-CaO-Al2O3 slags was studied at 1500° C and 1550 °C under an inert atmosphere of argon. The results show that the dissolution process is controlled by mass transfer of SiO2 in the slag. The experimental results were used to evaluate the dissolution rate, which was found to increase with increasing CaO/Al2O3 ratios as well as with increasing temperature. Boltzmann–Matano analysis was applied to obtain a profile-based effective chemical inter-diffusivity. The extracted inter-diffusivity coefficients decrease systematically with increasing SiO2 content and fall in the range of ~10-12 – 10-13 m2/s. These low values imply intrinsically slow diffusion-controlled SiO2 enrichment, so that approaching equilibrium is unlikely within the residence time of descending materials in industrial furnaces.

Aug 3, 2026

By S. Swanepoel, M. W. Erwee, Q. G. Reynolds, R. Fourie

Unexpected excursions in electrode hoist position are occasionally observed on direct-current arc furnace plants producing ferrochromium, and are not readily explained by changes in electrical power supply or known process disturbances. One possible mechanism for this is variations in feed reductant balance altering the freeboard gas composition and, hence, the thermophysical properties of the arc plasma, changing the arc's effective electrical resistance. This hypothesis is investigated using an integrated computational modelling workflow comprising thermochemical equilibrium simulations in FactSage, plasma property calculations using the open-source minplascalc tool, and magnetohydrodynamic arc simulations using the open-source plasmaArc solver. Three reductant balance conditions were examined across a range of effective slag temperatures. Results show that while the reductant balance does influence freeboard gas composition and certain plasma properties (particularly electrical conductivity and radiation emission coefficient when lower slag temperatures are considered), these two effects act in opposing directions and largely cancel one another. Arc voltages and resistances are consequently not significantly different between reductant conditions. It is concluded that variations in feed reductant balance are unlikely to be the primary cause of the observed hoist excursion events via this mechanism, and directions for future investigation are proposed.

Aug 3, 2026

By B. S. Xakalashe, M. Khama, Q. G. Reynolds

Pre-reducing chromite with hydrogen offers significant benefits, including reduced energy consumption in downstream smelting and lower carbon dioxide emissions. To leverage these advantages, it is essential to develop computational models that facilitate the design, optimisation, and control of the process. Full scale models such as 3D computational fluid dynamics models are often used to investigate the multi-scale flow physics in heterogeneous reactors. However, these models impose prohibitive computational expense in the modelling of heterogeneous reacting flow systems. The high computational expense prevents the use of high dimensional systems in real time control and online optimisation of reacting flow systems. In order to facilitate incorporation of predictive models in the heterogenous reacting flow systems control loop, computationally efficient reduced order models are required. Owing to these requirements, a reduced order model for pre-reduction of chromite with hydrogen was developed with the view to rapidly predict the performance indicators for pre-reduction of chromite with hydrogen. The Thiele modulus method was used to develop the reduced order model, and the model results were compared to isothermal pre-reduction experimental results at a range of pre-reduction temperatures from 1200 oC to 1400 oC. The model predicts the degree of reduction, diffusion of gases through the product layer, unreacted core radius of the grain radius, and local and global conversion. The final conversion across all temperatures as predicted by the reduced order model deviate from the experimentally calculated conversion by a maximum relative error of 2.7% while the initial conversions differ significantly, reaching a maximum error of 65%.

Aug 3, 2026

By R. Snodgrass, G. Marsden, K. van der Merwe, R. Hundermark

The Southern African Ni-Cu-PGM smelting industry has evolved significantly from 1937 to date. As demand for platinum group metals has increased, smelting technology development has been closely linked to the need to process more concentrate, but also to changes in the chemistry and mineralogy of concentrates from the various platinum group metals-containing reef types. Early technologies relied on blast furnaces and Great Falls converters, but from the late 1960s, electric furnaces and Peirce Smith converters were commissioned. In the early 1990s, the introduction of water-cooled copper plate coolers into the slag zones of the primary furnaces enabled greater power intensity and throughput, with further intensification from the early 2000s requiring the use of deep-cooled copper coolers. Converting technology was also modernised to include a top submerged lance converter in one instance. Approaches to converter slag cleaning have evolved from recycling slag to the primary furnaces, to milling and flotation or electric furnace slag cleaning as the Cr2O3 content in slags has increased. The shift in the 1990s from Merensky ore derived concentrates to those from UG2 ores impacted the process design for the primary furnaces, with UG2 concentrates having lower matte falls and higher Cr2O3 levels. Conversely, concentrates derived from Platreef and Great Dyke ores, with high matte falls and lower Cr2O3 levels, have introduced other challenges. Furnace designs and operating philosophies have been improved to better handle these ranges of concentrates, the resulting slags and superheated mattes, the containment of which is non-trivial. The smelting of non-roasted concentrates in the primary furnaces gave rise to rapid corrosion of the copper coolers, and triggered development of corrosion mitigation strategies. Advances in SO2 emissions control have transitioned from single contact sulphuric acid plants in the 1970s, to the adoption of double contact acid plants, tailgas, and dual-alkali scrubbing in the early 2000s. Low SO2 strength off-gas streams from primary furnaces are abated in some cases, with technologies such as the Sulphacid process introduced from the early 2000s and the Wet-gas Sulphuric Acid process from the early 2020s. With advances in process intensification, increases in operating temperatures and throughputs, and use of water cooling, consequences of furnace failures have become more severe. Water leaks into the molten material environment, primary furnace containment, and slag granulation have been particularly challenging. Technologies, operating, and maintenance philosophies have been developed for prevention and mitigation of failures, and the adoption of process safety management approaches has yielded systematic benefits. With the outlook in demand for PGMs changing as a function of automotive requirements, smelting technology will continue to evolve for further enhancement of safety and environmental protection, reduced costs, and greater efficiencies.

Aug 3, 2026

By M. Tadie, D. A. Barrett, B. von der Heyden, R. Cromarty

This paper investigated the prereduction of ferruginous manganese tailings from the Nchwaning mine by isothermal reduction between 650 °C and 1050 °C. The treated tailings underwent subsequent magnetic separation to upgrade the Mn/Fe ratio and manganese grade so that the tailings can be used as high-quality ferroalloy feedstock. The tailings contain recoverable manganese but is penalised by elevated and complex iron content. There is a high degree of mineralogical variability found in the untreated tailings. Iron is present both as hematite and in solid solution within manganese minerals such as bixbyite, braunite, and braunite II. A hydrogen atmosphere was used in this paper as it is sufficiently reducing to produce metallic iron that can be separated magnetically. Lime and silica additives were investigated to determine their influence on Fe reduction kinetics and globule formation, which impacts the separability of Fe and Mn. Optical microscopy and SEM analysis of the treated material revealed distinct metallurgical behaviour between iron reduced from hematite – forming larger globules (50 µm to 600 µm) – and iron reduced from Mn-hosted phases, which formed smaller globules (0.1 µm to 2 µm). Relatively milder reducing conditions achieved the highest Mn/Fe ratio of 4.52 and an Mn grade of 57 wt.%. While below the desired target specification (Mn/Fe of at least 7.5 wt.% and Mn grade of at least 44 wt.%), this can still be met by blending the product stream with other low-grade Mn ores that contain minimal Fe. These findings highlight the potential for the upgradation of ferruginous manganese tailings.

Aug 3, 2026